Quote:
Originally Posted by todesengel
I would also like to add that I do not buy magnaflows response to a restriction towards the tail end of the exhaust. It just seems contrary to theory.
First ask yourself what happens when exhaust gases cool, they expand. With expansion of gases it slows and requires more area to evacuate. For this reason you see a lot of people run 2.25"-2.50" headers which dump into a larger system down the line and/or a exhaust system that "megaphones" towards the tail end to compensate for the expansion of these gases as they cool. For this reason, imho, it would seem "better" to have a restriction on the front end, where the gases are still hot, than the back end. The "better" solution, again imho, is to have a consistent system OR one that expands to take into account the expansion of gases, OR the best solution which would be a system that is coated, or wrapped, to limit gas expansion AND enlarges towards the discharge.
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Well...Gasses do NOT expand as they cool; just the opposite (or a lot of thermal dynamics texts books got it all wrong!). Put the cap (seal) on an empty plastic milk jug at room temp and put it in the fridge, if ya wanna see for yourself.
But, I agree, from a fluid dynamics perspective, that a consistent size (i.e.) uniform throughout is important - as opposed to varying diameters abruptly (especially abruptly!) along the way
. Otherwise, there are acoustical energy consequences (turbulance being one byproduct); hence the funnel designs you see on some intake porting jobs, AND, (to your point) the same is true on some exhausts, tho not so much on anything but rice burners and...and tubas, of course. (Electronics engineers refer to the taper concept as "impedance matching" - a physical reality in waveguide design...But, I digress.)
P.